Imprinted bi-layer micro-structure method

ABSTRACT

A method of making an imprinted micro-wire structure includes providing a substrate having an edge area and a central area separate from the edge area and providing first, second, and third different stamps. A curable bottom, connecting layer, and top layer are formed on the substrate. A bottom-layer micro-channel is imprinted in the bottom layer in the central area and the edge area, a connecting-layer micro-channel is imprinted in the connecting layer in the edge area over the bottom-layer micro-channel, an edge micro-channel is imprinted in the top layer in the edge area over the connecting-layer micro-channel, and top-layer micro-channels are imprinted in the top layer over the central area. Micro-wires are formed in each micro-channel. The bottom-layer micro-wire in the central area is electrically connected to the edge micro-wire in the edge area and is electrically isolated from the top-layer micro-wire.

CROSS REFERENCE TO RELATED APPLICATIONS

Reference is made to commonly-assigned, co-pending U.S. patentapplication Ser. No. ______ (Kodak Docket K001585) filed concurrentlyherewith, entitled “Imprinted Bi-Layer Micro-Structure Method withBi-Level Stamp” by Cok; commonly-assigned, co-pending U.S. patentapplication Ser. No. ______ (Kodak Docket K001586) filed concurrentlyherewith, entitled “Imprinted Bi-Layer Micro-Structure” by Cok; commonlyassigned U.S. patent application Ser. No. ______ (Kodak Docket K001464)entitled “Imprinted Multi-Layer Micro-Structure Method” by Cok, thedisclosures of which are incorporated herein.

Reference is made to commonly assigned U.S. patent application Ser. No.13/862,679, filed Apr. 15, 2013, entitled “Hybrid Single-Side TouchScreen Method” by Burberry et al; and commonly assigned U.S. patentapplication Ser. No. 13/784,869, filed Mar. 5, 2013, entitled“Micro-Channel Structure with Variable Depths” by Cok, the disclosuresof which are incorporated herein.

FIELD OF THE INVENTION

The present invention relates to transparent electrodes havingelectrically conductive micro-wires formed in multiple layers.

BACKGROUND OF THE INVENTION

Transparent electrical conductors are widely used in the flat-paneldisplay industry to form electrodes that are used to electrically switchlight-emitting or light-transmitting properties of a display pixel, forexample in liquid crystal or organic light-emitting diode displays.Transparent conductive electrodes are also used in touch screens inconjunction with displays.

In such applications, the transparency and conductivity of thetransparent electrodes are important attributes. In general, it isdesired that transparent conductors have a high transparency (forexample, greater than 90% in the visible spectrum) and a low electricalresistivity (for example, less than 10 ohms/square).

Transparent conductive metal oxides are well known in the display andtouch-screen industries and have a number of disadvantages, includinglimited transparency and conductivity and a tendency to crack undermechanical or environmental stress. Typical prior-art conductiveelectrode materials include conductive metal oxides such as indium tinoxide (ITO) or very thin layers of metal, for example silver or aluminumor metal alloys including silver or aluminum. These materials arecoated, for example, by sputtering or vapor deposition, and arepatterned on display or touch-screen substrates, such as glass. Forexample, the use of transparent conductive oxides to form arrays oftouch sensors on one side of a substrate is taught in U.S. PatentPublication 2011/0099805 entitled “Method of Fabricating CapacitiveTouch-Screen Panel”.

Transparent conductive metal oxides are increasingly expensive andrelatively costly to deposit and pattern. Moreover, the substratematerials are limited by the electrode material deposition process (e.g.sputtering) and the current-carrying capacity of such electrodes islimited, thereby limiting the amount of power that can be supplied tothe pixel elements. Although thicker layers of metal oxides or metalsincrease conductivity, they also reduce the transparency of theelectrodes.

Transparent electrodes including very fine patterns of conductiveelements, such as metal wires or conductive traces are known. Forexample, U.S. Patent Publication No. 2011/0007011 teaches a capacitivetouch screen with a mesh electrode, as do U.S. Patent Publication No.2010/0026664, U.S. Patent Publication No. 2010/0328248, and U.S. Pat.No. 8,179,381, which are hereby incorporated in their entirety byreference. As disclosed in U.S. Pat. No. 8,179,381, fine conductorpatterns are made by one of several processes, including laser-curedmasking, inkjet printing, gravure printing, micro-replication, andmicro-contact printing. In particular, micro-replication is used to formmicro-conductors formed in micro-replicated channels. The transparentmicro-wire electrodes include micro-wires between 0.5μ and 4μ wide and atransparency of between approximately 86% and 96%.

Conductive micro-wires can be formed in micro-channels embossed in asubstrate, for example as taught in CN102063951, which is herebyincorporated by reference in its entirety. As discussed in CN102063951,a pattern of micro-channels is formed in a substrate using an embossingtechnique. Embossing methods are generally known in the prior art andtypically include coating a curable liquid, such as a polymer, onto arigid substrate. A pattern of micro-channels is embossed (impressed orimprinted) onto the polymer layer by a master having an inverted patternof structures formed on its surface. The polymer is then cured. Aconductive ink is coated over the substrate and into the micro-channels,the excess conductive ink between micro-channels is removed, for exampleby mechanical buffing, patterned chemical electrolysis, or patternedchemical corrosion. The conductive ink in the micro-channels is cured,for example by heating. In an alternative method described inCN102063951, a photosensitive layer, chemical plating, or sputtering isused to pattern conductors, for example, using patterned radiationexposure or physical masks. Unwanted material (e.g. photosensitiveresist) is removed, followed by electro-deposition of metallic ions in abath.

Conductive micro-wires are used to form a touch switch, for example, asillustrated in U.S. Patent Publication 2011/0102370. In this example, acapacitive touch switch includes a first substrate on which is formed afirst mesh-like electrode and a second substrate on which is formed asecond mesh-like electrode. The first and second substrates areintegrally bonded via an adhesive layer in such a manner that the firstand second mesh-like electrodes face each other. Such a design requiresthe use of two substrates that are aligned and bonded together.

Multi-level masks are used with photo-lithography to form thin-filmdevices, for example as disclosed in U.S. Pat. No. 7,202,179. Animprinted 3D template structure is provided over multiple thin filmsformed on a substrate. The multiple levels of the template structure areused as masks for etching the thin films. This approach requires the useof a mask and multiple photo-lithographic steps.

There is a need, therefore, for further improvements in micro-wirestructures for transparent electrodes that simplifies manufacturingsteps and provides more complex and interconnected patterns.

SUMMARY OF THE INVENTION

In accordance with the present invention, a method of making animprinted micro-wire structure comprises:

providing a substrate having an edge area and a central area separatefrom the edge area;

providing first, second, and third different stamps;

providing a curable bottom layer in relation to the substrate;

forming an imprinted bottom-layer micro-channel in the curable bottomlayer by at least imprinting the curable bottom layer with the firststamp in at least a portion of the central area and in at least aportion of the edge area and curing the curable bottom layer, thebottom-layer micro-channel extending from the central area into the edgearea;

locating a curable electrical conductor in the bottom-layermicro-channel and curing the curable electrical conductor to form abottom-layer micro-wire in the bottom-layer micro-channel, thebottom-layer micro-wire extending from the central area into the edgearea;

providing a curable connecting layer adjacent to and in contact with thecured bottom layer and the bottom-layer micro-wire;

forming an imprinted connecting-layer micro-channel in the curableconnecting layer by at least imprinting the curable connecting layerwith the second stamp over at least a portion of the bottom-layermicro-channel in at least a portion of the edge area and curing thecurable connecting layer;

forming a connecting-layer micro-wire in the connecting-layermicro-channel contacting at least a portion of the bottom-layermicro-wire;

providing a curable top layer adjacent to and in contact with the curedconnecting layer and the connecting-layer micro-wire;

forming an imprinted edge micro-channel in the curable top layer by atleast imprinting the curable top layer with the third stamp over atleast a portion of the connecting-layer micro-channel in at least aportion of the edge area and forming an imprinted top-layermicro-channel in the curable top layer by at least imprinting thecurable top layer with the third stamp separate from the bottom-layermicro-channel and over at least a portion of the bottom-layermicro-channel in at least a portion of the central area and curing thecurable top layer;

forming an edge micro-wire in the edge micro-channel contacting at leasta portion of the connecting-layer micro-wire and forming a top-layermicro-wire in the top-layer micro-channel that is electrically isolatedfrom the edge micro-wire, the connecting-layer micro-wire, and thebottom-layer micro-wire; and

wherein the bottom-layer micro-wire in the central area is electricallyconnected to the edge micro-wire in the edge area and is electricallyisolated from the top-layer micro-wire.

The present invention provides multi-layered micro-wire structures withimproved complexity, connectivity, and manufacturability. Themicro-wires of the present invention are particularly useful intransparent electrodes for capacitive touch screen and display devices.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent when taken in conjunction with the followingdescription and drawings wherein identical reference numerals have beenused to designate identical features that are common to the figures, andwherein:

FIG. 1 is a cross section of an embodiment of the present invention;

FIG. 2 is a plan view of the embodiment of the present inventioncorresponding to FIG. 1;

FIGS. 3A-3B are plan views illustrating various embodiments of thepresent invention having micro-wires with portions that extend primarilyin different directions;

FIG. 4 is a cross section illustrating an imprinting stamp useful in amethod of the present invention;

FIG. 5 is a cross section illustrating a multi-level imprinting stampuseful in a method of the present invention;

FIGS. 6A-6M are cross sections illustrating sequential steps in a methodof the present invention that forms the multi-wire structure of FIG. 1;

FIGS. 7A-7I are cross sections illustrating sequential steps in analternative method of the present invention that forms the multi-wirestructure of FIG. 1;

FIGS. 8A-8B are cross sections illustrating sequential optional stepsuseful for various methods of the present invention;

FIG. 9 is a flow diagram illustrating an embodiment of the presentinvention corresponding to the cross sections of FIGS. 6A-6M;

FIG. 10 is a flow diagram illustrating an embodiment of the presentinvention corresponding to the cross sections of FIGS. 7A-7I;

FIG. 11 is a plan view of another embodiment of the present inventioncorresponding to FIG. 1;

FIG. 12 is a plan view of yet another embodiment of the presentinvention corresponding to FIG. 1;

FIG. 13 is a plan view of an embodiment of the present invention; and

FIG. 14 is a cross section of another embodiment of the presentinvention.

The Figures are not drawn to scale since the variation in size ofvarious elements in the Figures is too great to permit depiction toscale.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed toward imprinted multi-layermicro-wire structures having electrically conductive micro-wires formedin micro-channel structures in multiple layers over a substrate. In anembodiment, the multi-layer structure is a bi-layer structure Imprintedstructures are also known to those skilled in the art as embossed orimpressed structures formed by locating an imprinting, impressing, orembossing stamp having protruding structural features in a curablelayer, curing the layer, and then removing the stamp to formmicro-channels corresponding to the structural features that are thenfilled with a conductive ink that is cured to form micro-wires.

Referring to FIG. 1 in cross section and to FIG. 2 in plan view,according to an embodiment of the present invention an imprintedmicro-wire structure 5 includes a substrate 10 with a bottom layer 12, aconnecting layer 14, and a top layer 16 formed in relation to thesubstrate 10. The connecting layer 14 is between the bottom layer 12 andthe top layer 16 so that the connecting layer 14 is adjacent to and incontact with the bottom layer 12 and the connecting layer 14 is alsoadjacent to and in contact with the top layer 16. The substrate 10includes an edge area 72 and a central area 70.

A bottom-layer micro-channel 50 is imprinted in the bottom layer 12 inat least a portion of the central area 70 and in at least a portion ofthe edge area 72, the bottom-layer micro-channel 50 extending from thecentral area 70 into the edge area 72. A bottom-layer micro-wire 52 islocated in the bottom-layer micro-channel 50 so that the bottom-layermicro-wire 52 likewise extends from the central area 70 into the edgearea 72. An imprinted connecting-layer micro-channel 30 is in contactwith at least a portion of the bottom-layer micro-wire 52 in at least aportion of the edge area 72. A connecting-layer micro-wire 32 is locatedin the connecting-layer micro-channel 30 contacting at least a portionof the bottom-layer micro-wire 52. An imprinted edge micro-channel 40 isin the top layer 16 in at least a portion of the edge area 72 contactingat least a portion of the connecting-layer micro-wire 32. Top-layermicro-channels 20 are also in the top layer 16 in at least a portion ofthe central area 70 and are separate from the edge micro-channel 40 andthe bottom-layer micro-channel 50. An edge micro-wire 42 is located inthe edge micro-channel 40 contacting at least a portion of theconnecting-layer micro-wire 32. Top-layer micro-wires 22 are located inthe top-layer micro-channels 20 and are separate from both the edgemicro-wire 42 and the bottom layer micro-wire 52. The edge micro-wire 42is electrically connected to the bottom-layer micro-wire 52 through theconnecting-layer micro-wire 32 and is electrically isolated from thetop-layer micro-wire 22.

In another embodiment of the present invention, the connecting layer 14and the top layer 16 are a single multi-layer 15. Similarly, in anembodiment, edge micro-channel 40 and connecting-layer micro-channel 30are a single multi-layer micro-channel 41 and edge micro-wire 42 andconnecting-layer micro-wire 32 are a single multi-layer micro-wire 43.

Micro-wires illustrated in the Figures are formed in micro-channels andare therefore not readily distinguished in the illustrations. Forclarity, the micro-channels in which the micro-wires are formed arelabeled with corresponding numbered arrows pointing to themicro-channels; the micro-wires formed in the correspondingmicro-channels are labeled with numbered lead lines touching themicro-wires.

The substrate 10 is adjacent to the bottom layer 12 so that thebottom-layer micro-wire 52 is formed in a layer adjacent to thesubstrate 10 and the top-layer micro-wires 22 are formed in a layerfarther from the substrate 10. In such an embodiment, the bottom layer12 and the bottom-layer micro-wire 52 is formed on or over the substrate10; the connecting layer 14 and the connecting-layer micro-wire 32 areformed on or over the bottom layer 12 and the bottom-layer micro-wire52; and the top layer 16 and the top-layer micro-wires 22 are formed onor over the connecting layer 14 and the connecting-layer micro-wire 32.In an embodiment, the bottom layer 12 and bottom-layer micro-wire 52 isformed first, then the connecting layer 14 and connecting-layermicro-wire 32 is formed, and then the top layer 16 and top-layermicro-wires 22 and edge micro-wire 42 are formed.

In various embodiments of the present invention, the bottom, connecting,or top layers 12, 14, 16 include common materials or are formed fromcommon materials. In an embodiment, the bottom, connecting, or toplayers 12, 14, and 16 are not distinguishable apart from themicro-channels or micro-wires formed within the bottom, connecting, ortop layers 12, 14, and 16. Thus, the bottom layer 12 and connectinglayer 14 form a common layer, or the connecting layer 14 and the toplayer 16 form a common layer, or the bottom, connecting, and top layers12, 14, and 16 form a common layer. In a useful embodiment, the bottomlayer 12 is cross-linked to the connecting layer 14, the connectinglayer 14 is cross linked to the top layer 16, or the bottom, connecting,and top layers 12, 14, and 16 are cross linked to each other. In anembodiment, the bottom layer 12, the connecting layer 14, and the toplayer 16 are cured layers. For example, the bottom, connecting, and toplayers 12, 14, and 16 are cured layers formed from a curable polymerthat includes cross-linking agents that are cured with heat or exposureto radiation, such as ultra-violet radiation.

In further embodiments of the present invention, the bottom-layermicro-wire 52, the connecting-layer micro-wire 32, the edge micro-wire42, or the top-layer micro-wire 22 is a cured micro-wire, for example acured conductive ink. In an embodiment, a common conductive ink is usedfor any of the bottom-layer micro-wire 52, the connecting-layermicro-wire 32, the edge micro-wire 42, or the top-layer micro-wires 22so that they include common materials or are formed from commonmaterials. Useful, cured conductive inks can include electricallyconductive particles, for example, silver nano-particles that aresintered, welded, or agglomerated together.

In an embodiment, the connecting-layer micro-wire 32 and thebottom-layer micro-wire 52 are a common micro-wire so that electricallyconductive particles in the bottom-layer micro-wire 52 are sintered,welded, or agglomerated to electrically conductive particles in theconnecting-layer micro-wire 32. Such a structure is formed if thebottom-layer micro-wire 52 and the connecting-layer micro-wire 32 arecoated as a curable conductive ink and at least partially cured in acommon step. Alternatively, the connecting-layer micro-wire 32 and theedge micro-wire 42 are a common micro-wire so that electricallyconductive particles in the connecting-layer micro-wire 32 are sintered,welded, or agglomerated to electrically conductive particles in the edgemicro-wire 42. Such a structure is formed if the edge micro-wire 42 andthe connecting-layer micro-wire 32 are coated as a curable conductiveink and at least partially cured in a common step. In a furtherembodiment, the edge micro-wire 42, the connecting-layer micro-wire 32,and the bottom-layer micro-wire 52 are a common micro-wire and includecommon materials.

In an embodiment, electrical connectors or connecting wires 62 areelectrically connected to edge micro-wires 42 formed in the top layer16. Such connections can provide electrical power to the bottom-layermicro-wire 52. Electrical connections can also be made to the top-layermicro-wires 22.

As illustrated in FIG. 2, the substrate 10 has at least one firstsubstrate edge 74 and the edge area 72 is adjacent to the firstsubstrate edge 74. A portion of the edge micro-wire 42 or multi-levelmicro-wire 43 forms at least a portion of a row connection pad 60A inthe edge area 72. In an embodiment, a plurality of edge micro-wires 42is electrically connected through a corresponding plurality ofconnecting-layer micro-wires 32 to a corresponding plurality ofbottom-layer micro-wires 52. Alternatively, a plurality of multi-layermicro-wires 43 are electrically connected to a corresponding pluralityof bottom-layer micro-wires 52. Similarly, the imprinted micro-wirestructure of the present invention can include a plurality of top-layermicro-wires 22 electrically isolated from the edge micro-wires 42,connecting-layer micro-wires 32, and bottom-layer micro-wires 52, or themulti-layer micro-wires 43.

In another embodiment, and as illustrated in FIG. 2, the substrate 10has at least first and second substrate edges 74, 76 and at least someof the plurality of edge micro-wires 42 are located in an edge area 72adjacent to the first substrate edge 74 and at least some of theplurality of top-layer micro-wires 22 extend into a second edge area 73adjacent to the second substrate edge 76 and separate from the centralarea 70. In such an embodiment, the edge micro-wires 42 form horizontalconductors that extend to row connection pads 60A in edge area 72adjacent to the first substrate edge 74 and the top-layer micro-wires 22form vertical conductors that extend to column connection pads 60B insecond edge area 73 adjacent to the second substrate edge 76. As will beappreciated by those knowledgeable in the art, the relative locations ofhorizontal and vertical electrodes can be exchanged.

Referring to the plan views of FIGS. 11 and 12, an imprinted micro-wirestructure 5 of the present invention includes a plurality of top-layermicro-wires 22 and edge micro-wires 42 formed in top layer 16 (or themulti-layer 15, not shown). The edge micro-wires 42 include rowconnection pads 60A formed in the edge area 72 separate from the centralarea 70. Connecting-layer micro-wires 32 electrically connectbottom-layer micro-wires 52 to the edge micro-wires 42. In thisembodiment, the edge micro-wires 42 are in the edge area 72 and thetop-layer micro-wires 22 also extend into the same edge area 72 adjacentto the same first substrate edge 74. By adjacent is meant that no otherelement is between two adjacent elements. In such an embodiment, forexample, a single connector can electrically connect to both the edgemicro-wires 42 and to the top-layer micro-wires 22 with row connectionpads 60A. As shown in FIG. 11, the edge micro-wires 42 are adjacent toeach other and the top-layer micro-wires 22 are likewise adjacent toeach other. In the alternative design of FIG. 12, the edge micro-wires42 are interdigitated between the top-layer micro-wires 22. In such anembodiment, central top-layer micro-wires 22 can cross other top-layermicro-wires 22 with a micro-wire bridge 78. Alternatively, the centraltop-layer micro-wires 22 can loop over the top of other top-layermicro-wires 22 and pass a second time over some of the bottom-layermicro-wires 52 before entering the edge area 72 (not shown).

Referring next to FIGS. 3A-3B, structures useful for enabling electricalcontact between micro-wires in different layers are illustrated.Referring first to FIG. 3A, a portion of the edge micro-wire 42 extendsprimarily in a direction D2 different from the direction D1 in which atleast a portion of the connecting-layer micro-wire 32 and top-layermicro-wire 22 primarily extend. In some embodiments, the direction D2 inwhich at least a portion of the edge micro-wire 42 primarily extends isorthogonal to the direction D1 in which at least a portion of theconnecting-layer micro-wire 32 primarily extends. In another embodiment,and as is illustrated in FIG. 3A, at least a portion of theconnecting-layer micro-wire 32 extends primarily in a direction D1different from the direction D2 in which at least a portion of thebottom-layer micro-wire 52 primarily extends.

By primarily extends is meant that for micro-wires that have an aspectratio other than one for a portion of the micro-wire, for examplerectangular non-square micro-wires, the longer side of the micro-wireportion has an edge that extends in the primary direction of themicro-wire portion. Alternatively, most micro-wires are long and narrow;the length direction of the micro-wire is the direction in which themicro-wire primarily extends.

The structure in FIG. 3A is useful in preventing problems withelectrical connectivity between micro-wires in different layers causedby registration or alignment tolerance requirements by extending theregion over which a micro-wire in one layer can electrically contact amicro-wire in another layer. This reduces the alignment tolerancerequirements for the location of micro-wires in different layers. Forexample, referring to FIG. 3B, if the connecting-layer micro-wire 32,edge micro-wire 42, or the bottom-layer micro-wire 52 are mis-alignedwith respect to each other, electrical contact is still made between theedge micro-wire 42 and the bottom-layer micro-wire 52. As shown in FIG.3B, the connecting-layer micro-wires 32 is mis-aligned with respect tothe bottom-layer micro-wire 52, and the edge micro-wire 42 ismis-aligned with respect to the connecting-layer micro-wire 32. Despitethese mis-alignments, the bottom-layer micro-wire 52 is electricallyconnected to the edge micro-wire 42, as desired.

Micro-wires of the present invention are not limited to rectangles.Micro-wires can be curved or form rings or waves and can also aid inconnecting micro-wires in different layers in the presence ofmis-alignment between micro-channels in the different layers.

Referring to FIG. 13, in another useful embodiment of an imprintedmicro-wire structure 5, micro-wires are patterned in electricallyinter-connecting grids forming apparently transparent electrodes. Asshown in FIG. 13, top-layer micro-wires 22 are patterned into anelectrically interconnected grid forming separate top electrodes 26. Theedge micro-wires 42 and the connecting-layer micro-wires 32 can alsoeach include a plurality of micro-wires as can the row and columnconnection pads 60A, 60B. Connecting wires 62 are electrically connectedto each row or column connection pad 60A, 60B. Thus, bottom-layermicro-wires 52, connecting-layer micro-wires 32, and edge micro-wires 42are patterned into an electrically interconnected grid forming separatebottom electrodes 46. The bottom electrodes 46 form row electrodes thatextend from the central area 70 into the first edge area 72 with rowconnection pads 60A. The top electrodes 26 form column electrodes thatextend from the central area 70 into the second edge area 73 with columnconnection pads 60B. The top and bottom electrodes 26, 46 can extend indifferent directions to form a two-dimensional array of overlappingmicro-wire electrodes that make up an array of capacitors.

In an embodiment, the structure illustrated in FIG. 13 forms acapacitive touch screen. The bottom-layer micro-wires 52 patterned intobottom electrodes 46 and the top-layer micro-wires 22 patterned into topelectrodes 26 overlap to form an array of capacitors whose capacitanceis sensed through edge micro-wires 42. A controller (not shown)electrically connected to the connecting wires 62 can control thecapacitive touch screen.

In a further embodiment of the present invention, illustrated in FIG.14, the multi-layer imprinted micro-wire structure 5 is extended to morethan two layers. Referring to FIG. 14, a substrate 10 has the bottomlayer 12 coated thereon with bottom-layer micro-wires 52 formed in thebottom layer 12. A connecting mid-layer 18 is coated over the bottomlayer 12 and bottom-layer micro-wire 52 and imprinted with a stamp toform a micro-channel in contact with the bottom-layer micro-wire 52 thatis filled with a connecting-layer micro-wire 32. A mid-layer 19 iscoated over the connecting mid-layer 18 and imprinted with a stamp toform micro-channels that are filled to construct a mid-layer micro-wire54 and another connecting-layer micro-wire 32. A connecting-layer 14 iscoated over the mid-layer 19 and imprinted with a stamp to formmicro-channels that are filled to construct a connecting-layermicro-wire 32 and another connecting mid-layer micro-wire 34. The toplayer 16 is then coated over the mid-layer 19, connecting-layermicro-wire 32, and connecting mid-layer micro-wire 34, imprinted with astamp to form micro-channels that are filled to construct the edgemicro-wires 42, a second edge micro-wire 44, and top-layer micro-wires22. Thus, electrically isolated micro-wire patterns are formed in threeseparate layers and each electrically connected with micro-wires in thetop layer 16 to enable electrical connection to a connecting wire andcontroller. The edge micro-wire 42 is located in edge area 72, thesecond edge micro-wire 44 is located in the second edge area 73, and thetop-layer micro-wires 22 are in the central area 70. Such structures canbe built either with or without multi-level stamps, as discussed furtherbelow.

Referring to FIG. 9 and to FIGS. 6A-6M, in a method of the presentinvention, a substrate 10 as illustrated in FIG. 6A is provided in step100. First, second, and third different stamps are provided in step 105.Referring also to FIG. 4, a first stamp 80 has one or more protrusions89 that, when located in a curable layer, form micro-channels. In step110 and as illustrated in FIG. 6B, a curable bottom layer 12 is providedin relation to the substrate 10, for example by coating a layer ofcurable material on the substrate 10 or on layers formed on thesubstrate 10.

Referring next to FIG. 6C, bottom-layer micro-channel 50 is formed inthe curable bottom layer 12 by at least imprinting the curable bottomlayer 12 with the first stamp 80 located so that protrusion 89 extendsinto the curable bottom layer 12 over the substrate 10 in step 115. Thecurable bottom layer 12 is cured, for example with radiation 90, in step120 and the first stamp 80 is removed from the cured bottom layer 12(FIG. 6D) so that bottom-layer micro-channel 50 is formed in the curedbottom layer 12 over the substrate 10.

A conductive ink is provided in the bottom-layer micro-channel 50 instep 130, for example by coating the cured bottom layer 12 withconductive ink and wiping excess conductive ink from the surface of thecured bottom layer 12. The conductive ink is cured in step 135 to form abottom-layer micro-wire 52 in the bottom-layer micro-channel 50 in curedbottom layer 12 over substrate 10, as illustrated in FIG. 6E.

Referring to FIG. 6F, a curable connecting layer 14 is provided in step210 adjacent to and in contact with the cured bottom layer 12 and thebottom-layer micro-wire 2 over the substrate 10. Referring to FIG. 6G,the curable connecting layer 14 is imprinted in step 215 with a secondstamp 86 having a protrusion 89 located over at least a portion of thebottom-layer micro-channel 50 and bottom-layer micro-wire 52. Thecurable connecting layer 14 is cured in step 220, for example withradiation 90, and the second stamp 86 is removed. Referring to FIG. 6H,an imprinted connecting-layer micro-channel 30 is formed in the curedconnecting layer 14 over at least a portion of the bottom-layermicro-channel 50 and the bottom-layer micro-wire 52.

A conductive ink is provided in the connecting-layer micro-channel 30 instep 230 (FIG. 9), for example by coating the cured connecting layer 14with conductive ink and wiping excess conductive ink from the surface ofthe cured connecting layer 14. The conductive ink is cured in step 235to form a connecting-layer micro-wire 32 in the connecting-layermicro-channel 30 in the cured connecting layer 14 over the cured bottomlayer 12 over the substrate 10, as illustrated in FIG. 6I. Theconnecting-layer micro-wire 32 is in electrical contact with thebottom-layer micro-wire 52.

Referring next to FIG. 6J, a curable top layer 16 is provided in step310 adjacent to and in contact with the cured connecting layer 14 andthe connecting-layer micro-wire 32. The curable top layer 16 is on aside of the cured connecting layer 14 opposite the cured bottom layer12, the bottom-layer micro-wire 52, and the substrate 10. Referring toFIG. 6K, the curable top layer 16 is imprinted in step 315 with a thirdstamp 87 having protrusions 89, one of which is located over at least aportion of the connecting-layer micro-channel 30 and connecting-layermicro-wire 32 forming edge micro-channel 40. One or more otherprotrusions 89 extend over the bottom-layer micro-wire 52 formingtop-layer micro-channels 20. The curable top layer 16 is cured in step320, for example with radiation 90, and the third stamp 87 removed.Referring to FIG. 6L, an imprinted edge micro-channel 40 is formed incured top layer 16 over the cured connecting layer 14 and the substrate10, over at least a portion of the connecting-layer micro-channel 30,and over at least a portion of the connecting-layer micro-wire 32. Thetop-layer micro-channels 20 are separate from the edge micro-channel 40and the bottom-layer micro-wire 52 formed in the cured bottom layer 12over the substrate 10. The edge micro-channel 40 can, but need not,extend over the bottom-layer micro-wire 52.

A conductive ink is provided in the edge micro-channel 40 and top-layermicro-channels 20 in step 330, for example by coating the cured toplayer 16 with conductive ink and wiping excess conductive ink from thesurface of the cured top layer 16. The conductive ink is cured in step335 to form an edge micro-wire 42 in the edge micro-channel 40 andtop-layer micro-wires 22 in the top-layer micro-channels 20 in the curedtop layer 16 over the cured connecting layer 14 and opposite the curedbottom layer 12 and the substrate 10, as illustrated in FIG. 6M. Edgemicro-wire 42 is in electrical contact with connecting-layer micro-wire32 and bottom-layer micro-wire 52. Top-layer micro-wires 22 areelectrically isolated from (not in electrical contact with) thebottom-layer micro-wire 52.

In a further embodiment of the present invention, the step 215 offorming the imprinted connecting-layer micro-channel 30 further includescontacting the bottom-layer micro-wire 52 with the second stamp 86protrusion 89. By contacting the bottom-layer micro-wire 52 with thesecond stamp 86, material of the connecting layer 14 is removed from thecontacted area of the connecting-layer micro-wire 32 so that theconnecting-layer micro-wire 32 can electrically connect with thebottom-layer micro-wire 52. Similarly, the step 315 of forming theimprinted edge micro-channel 40 further includes contacting theconnecting-layer micro-wire 32 with protrusions 89 of the imprintingthird stamp 87. By contacting the connecting-layer micro-wire 32 withthe imprinting third stamp 87, material of the top layer 16 is removedfrom the contacted area of the connecting-layer micro-wires 32 so thatthe connecting-layer micro-wire 32 can electrically connect with theedge micro-wire 42.

In an alternative or additional embodiment illustrated in FIGS. 8A and8B, residual material in the connecting-layer micro-channel 30 in theconnecting layer 14 (or top-layer micro-channel 20 in the top layer 16)is removed to clear the surface of the bottom-layer micro-wire 52 in thebottom layer 12. Referring to FIG. 8A, the bottom layer 12 includes thebottom-layer micro-wire 52 formed over the substrate 10. The connectinglayer 14 has imprinted connecting-layer micro-channel 30 formed on thebottom layer 12 and the bottom-layer micro-wire 52. However, as shown inFIG. 8A, it is possible that material over the bottom-layer micro-wire52 remains in the connecting-layer micro-channel 30. For example, it canbe difficult to exactly locate the imprinting stamps precisely incontact with an underlying layer, or it can be preferred not to, sincesuch contact can cause deformation of the stamp or the layer that thestamp is imprinting. If this residual material stays in place, it canprevent electrical contact between bottom-layer micro-wire 52 andsubsequently formed connecting-layer micro-wire 32. Therefore, referringto FIG. 8B, an additional and optional etch step 225 is performed usinga plasma 92 to etch the residual material. The plasma 92 contains oxygenas an etchant gas to remove the organic material. As shown in FIG. 8B,the plasma 92 removes a portion of the connecting layer 14 to clear theconnecting-layer micro-channels 30 so that portions of the bottom-layermicro-wire 52 in the bottom layer 12 over the substrate 10 are exposed.

The plasma 92 removes a thinning depth 94 (FIG. 8A) of the entireconnecting layer 14 and it is therefore helpful to remove only enough ofthe connecting layer 14 to clear the connecting-layer micro-channels 30without exposing the bottom-layer micro-wire 52 to avoid an electricalshort between the bottom-layer micro-wire 52 and any top-layermicro-wires 22 (not shown) formed in top-layer micro-channels 20 overthe bottom-layer micro-wire 52. Thus, to prevent unwanted electricalshorts between micro-wires in adjacent layers, the thinning depth 94 isless than the difference between the depth of the cured connecting ortop layers 14, 16 and the depth of any micro-channels in thecorresponding cured connecting or top layer 14, 16.

The use of plasma 92 to remove a portion of a layer to clear amicro-channel can be used after any imprinting step that forms amicro-channel over an underlying micro-wire. Thus, step 225 is performedafter the imprinting step 215 to clear the connecting-layermicro-channel 30 and step 325 is performed after step 315 to clear theedge micro-channel 40.

In embodiments of the present invention, the material used in any of thebottom, connecting, or top layers 12, 14, 16 are the same. The bottom,connecting, or top layers 12, 14, 16 can include cross-linking materialand the material in each layer are cross linked by curing the material,for example through heat or radiation, or both.

Thus, in an embodiment, the curable bottom layer 12 includes firstcurable material and the first stamp 80 is located in contact with thefirst curable material and the first curable material is at least oronly partially cured to form the bottom-layer micro-channel 50. Thecurable connecting layer 14 includes second curable material and thesecond stamp 86 is located in contact with the second curable materialand the second curable material is at least or only partially cured toform the connecting-layer micro-channel 30. The curable top layer 16includes third curable material and the third stamp 87 is located incontact with the third curable material and the third curable materialis at least or only partially cured to form the edge and top-layermicro-channels 40, 20.

Furthermore, according to embodiments of the present invention, thebottom layer 12 is cross linked to the connecting layer 14 by onlypartially curing the bottom layer 12 in step 120 and further curing boththe bottom layer 12 and the connecting layer 14 in step 220 (FIG. 9). Itis also possible to cross link the connecting layer 14 to the top layer16 by only partially curing the connecting layer 14 in step 220 andfurther curing both the connecting layer 14 and the top layer 16 in step320 (FIG. 9).

When two adjacent layers include similar or the same materials and thematerials in the adjacent layers are cross linked to each other, theadjacent layers can be indistinguishable or inseparable. Thus, adjacentcross-linked layers can form a single layer and the present inventionincludes single layers that include multiple cross-linked layers withinthe single layer. The multiple layers can be coated with similarmaterials in separate operations and then form a single layer that iscured or cross-linked in a single step.

The micro-wires in each layer can be formed by coating the layer with aconductive ink, removing excess ink from the surface of the layer,leaving ink in the micro-channels in the layer, and then curing theconductive ink to form a micro-wire. In some cases, removing excess inkfrom the surface of the layer can also remove ink from themicro-channels. Therefore, in a further embodiment, conductive ink isdeposited in the bottom-layer micro-channel 50, the connecting-layermicro-channel 30, the edge micro-channel 40, or the top-layermicro-channels 20 a second time. Conductive ink located in amicro-channel a first time can be partially cured before locatingconductive ink in the micro-channel a second time, and the conductiveinks cured together in a second curing step to form a single micro-wire.

Therefore, a method of the present invention includes depositingconductive ink in the bottom-layer micro-channel 50 and at least or onlypartially curing the conductive ink to form the bottom-layer micro-wire52, further includes depositing conductive ink in the connecting-layermicro-channel 30 and at least or only partially curing the conductiveink to form the connecting-layer micro-wire 32, or further includesdepositing conductive ink in the edge micro-channel 40 and at least oronly partially curing the conductive ink to form the edge micro-wire 42.

According to another embodiment, conductive ink located inmicro-channels in different layers that are in contact are cured in acommon step to form a single micro-wire that extends through multiplemicro-channels and multiple layers. Thus, the edge micro-wire 42, theconnecting-layer micro-wire 32, and the bottom-layer micro-wire 52 areat least partially cured in a single step to form a single micro-wire.Furthermore, if the conductive ink includes electrically conductiveparticles, the electrically conductive particles in the edge micro-wire42 and the electrically conductive particles in the connecting-layermicro-wire 32 are sintered, welded, or agglomerated together in a singlecuring step. Similarly, electrically conductive particles in theconnecting-layer micro-wire 32 are sintered, welded, or agglomerated tothe electrically conductive particles in the bottom-layer micro-wire 52.

Thus, a method of the present invention can include depositing firstconductive ink in the bottom-layer micro-channel 50 and only partiallycuring the first conductive ink to form the bottom-layer micro-wire 52,depositing second conductive ink in the connecting-layer micro-channel30 and at least partially curing both the first and the secondconductive inks at the same time to form the bottom-layer micro-wire 52and the connecting-layer micro-wire 32. The first and second conductiveinks can include electrically conductive particles and the electricallyconductive particles in the first conductive ink are sintered, welded,or agglomerated to the electrically conductive particles in the secondconductive ink.

Similarly, a method of the present invention includes depositing firstconductive ink in the connecting-layer micro-channel 30 and onlypartially curing the first conductive ink to form the connecting-layermicro-wires 32, depositing second conductive ink in the edgemicro-channel 40 and at least partially curing the first and the secondconductive inks at the same time to form the edge micro-wire 42 andconnecting-layer micro-wire 32. The first and second conductive inks caninclude electrically conductive particles and the electricallyconductive particles in the first conductive ink are sintered, welded,or agglomerated to the electrically conductive particles in the secondconductive ink.

The embodiments of the present invention illustrated in FIGS. 6A-6M usethree stamps to imprint three layers of micro-channels in three steps aswell as using three separate steps to form the micro-wires in themicro-channels formed in the various layers. According to anotherembodiment of the present invention, a multi-level second stamp 82illustrated in FIG. 5 is used to form two levels of the imprintedmicro-wire structure 5 in a single, common step at the same time.Referring to FIG. 5, a multi-level second stamp 82 has at least one deepprotrusion 81 having a deep-protrusion depth 84 and at least one shallowprotrusion 83 having a shallow-protrusion depth 85. The deep-protrusiondepth 84 is greater than the shallow-protrusion depth 85 so that whenthe multi-level second stamp 82 is used to imprint a pattern in a layer,the portion of the pattern corresponding to the deep protrusion 81 isdeeper than the portions of the pattern corresponding to the shallowprotrusions 83.

Referring to FIGS. 7A-7I and to FIG. 10, another method of making animprinted micro-wire structure 5 corresponding to FIG. 1 includesproviding a substrate 10 (FIG. 7A) in step 100. A first stamp 80 and adifferent multi-level second stamp 82 are provided in step 106, themulti-level second stamp 82 having at least one deep protrusion 81 andone or more shallow protrusions 83, the first and second deepprotrusions 81 having a deep-protrusion depth 84 greater than ashallow-protrusion depth 85 of the shallow protrusion(s) 83, asillustrated in FIG. 5.

A curable bottom layer 12 is formed over the substrate 10 in step 110(FIG. 7B). The curable bottom layer 12 on the substrate 10 is imprintedwith the first stamp 80 (step 115) and cured (step 120), for examplewith radiation 90, as illustrated in FIG. 7C to form the bottom-layermicro-channel 50 in the curable bottom layer 12 on substrate 10 (FIG.7D).

Conductive ink is deposited in the bottom-layer micro-channels 50 (step130) and cured (step 135), forming the bottom-layer micro-wire 52 in thebottom-layer micro-channel 50 in the bottom layer 12 (FIG. 7E) over thesubstrate 10.

A curable multi-layer 15 is formed adjacent to and in contact with thecured bottom layer 12 and the bottom-layer micro-wire 52 over thesubstrate 10 in step 410 (FIG. 7F), for example by coating. In thisembodiment, the multi-layer 15 is a single layer that forms both theconnecting layer 14 and the top layer 16 of FIG. 1, and thecorresponding structures in the connecting layer and the top layer 14,16 are made in common steps.

The curable multi-layer 15 is imprinted with the multi-level secondstamp 82 in step 415 and cured in step 420 (FIG. 7G), for example withradiation 90. The imprinting is done over the bottom-layer micro-wire 52in the bottom layer 12 and over the substrate 10. Referring also to FIG.7H, a multi-layer micro-channel 41 and a top-layer micro-channel 20 inthe curable multi-layer 15 are formed in a common step by imprintingwith the multi-level second stamp 82. The multi-layer micro-channel 41includes the edge micro-channel 40 of FIG. 1 and the connecting-layermicro-channel 30 of FIG. 1. Although in the method described withrespect to FIGS. 6A-6M, the edge micro-channel 40 and theconnecting-layer micro-channel 30 are formed in separate steps and formseparate structures, in the method of FIGS. 7A-7I, the edgemicro-channel 40 and the connecting-layer micro-channel 30 are formed asa single multi-layer micro-channel 41 in a single step.

The portion of the multi-layer micro-channel 41 formed by the deepprotrusion 81 of the multi-level second stamp 82 is located over and incontact with at least a portion of the bottom-layer micro-wire 52. Thetop-layer micro-channels 20 formed by the shallow protrusions 83 of themulti-level second stamp 82 extend over at least a portion of thebottom-layer micro-wire 52 without contacting the bottom-layermicro-wire 52.

Conductive ink is deposited in the multi-layer micro-channel 41 andtop-layer micro-channel 20 (step 430) and cured (step 435), forming animprinted micro-wire structure 5 having a top-layer micro-wire 22 in thetop-layer micro-channel 20 and a multi-layer micro-wire 43 in themulti-layer micro-channel 41, as shown in FIG. 7I. The top-layermicro-wire 22 is electrically isolated from the multi-layer micro-wire43 and the bottom-layer micro-wire 52. The bottom-layer micro-wire 52 iselectrically connected to the multi-layer micro-wire 43 (that includesthe edge micro-wire 42 and connecting-layer micro-wire 32 of FIG. 1).

In one embodiment, the step 415 of forming the imprinted multi-layermicro-channel 41 includes contacting the bottom-layer micro-wire 52 withthe deep protrusion 81 of the multi-level second stamp 82.

Referring to FIGS. 8A and 8B in further embodiments of the presentinvention relevant to the structures and method of FIGS. 7A-7I, aportion of the cured multi-layer 15 is removed before the multi-layer 15is coated, for example by treating (step 425) the portion of the curedmulti-layer 15 with plasma 92. The treatment can thin the entire curedmulti-layer 15 by a thinning depth less than the deep-protrusion depth84 of the deep protrusion minus the shallow-protrusion depth 85 of theshallow protrusion.

In other embodiments, the bottom layer 12 and multi-layer 15 includecross-linkable material and the cross-linkable bottom-layer material iscross-linked to the cross-linkable multi-layer material, for example byUV exposure to resins as is known in the art. Such cross-linking betweenthe layers is accomplished when the curable bottom layer 12 includesfirst curable material and the first stamp 80 is located in contact withthe first curable material. The first curable material is at least oronly partially cured so that when the curable multi-layer 15 includessecond curable material and the multi-level second stamp 82 is locatedin contact with the second curable material, the step of at leastpartially curing the second curable material can also at least partiallycure the first material and cross link the first and second curablematerials in a common step. Such partial curing of individual curablematerial layers followed by curing multiple curable material layerstogether can form a single indistinguishable or inseparable layer,especially when the first and second materials are the same material,thus providing a stronger and more robust layer structure.

In a further embodiment, conductive ink is deposited in the multi-layermicro-channel 41 and the top-layer micro-channels 20 in a common step.In an alternative embodiment, conductive ink is deposited in thebottom-layer micro-channel 50, the multi-layer micro-channel 41, ortop-layer micro-channels 20 a second time and cured.

Furthermore, first conductive ink is deposited in the bottom-layermicro-channel 50 and at least or only partially cured. Second conductiveink is deposited in the multi-layer micro-channel 41 and top-layermicro-channels 20. The first conductive ink in the bottom-layermicro-channel 50 is at least partially cured in a common step with thesecond conductive ink in the multi-layer micro-channel 41.

The first and second conductive inks can each include electricallyconductive particles. In a further embodiment, the electricallyconductive particles in the second conductive ink are sintered, welded,or agglomerated to the electrically conductive particles in the firstconductive ink, thus improving their conductivity and the electricalconductivity of the junctions between the different-layer micro-wires.Indeed, the micro-wires in the different layers can be considered as acommon micro-wire.

In an embodiment, a cured-layer depth of the bottom layer 12, connectinglayer 14, or top layer 16 has a range of about one micron to twentymicrons and a cured-layer depth of the multi-layer 15 has a range ofabout 2 microns to 30 microns.

Cured bottom layer 12, connecting layer 14, top layer, 16, ormulti-layer 15 is a layer of curable material that has been cured and,for example, formed of a curable material coated or otherwise depositedon a surface, for example a surface of substrate 10, to form a curablelayer. The substrate-coated curable material is considered herein to becurable layer before it is cured and a cured layer after it is cured.Similarly, a cured electrical conductor is an electrical conductorformed by locating a curable material in a micro-channel and curing thecurable material to form the cured electrical conductor in themicro-channel. The cured electrical conductor is a micro-wire.

In various embodiments, curable layers are deposited as a single layerin a single step using coating methods known in the art, e.g. curtaincoating. In an alternative embodiment, curable layers are deposited asmultiple sub-layers using multi-layer deposition methods known in theart, e.g. multi-layer slot coating, repeated curtain coatings, ormulti-layer extrusion coating. In yet another embodiment, curable layersinclude multiple sub-layers formed in different, separate steps, forexample with a multi-layer extrusion, curtain coating, or slot coatingas is known in the coating arts. Micro-channels are embossed and curedin curable layers in a single step and micro-wires are formed bydepositing a curable conductive ink in micro-channels and curing thecurable conductive ink to form an electrically conductive micro-wire.

Cured layers (e.g. bottom, connecting, or top layers 12, 14, 16, ormulti-layer 15) useful in the present invention can include a curedpolymer material with cross-linking agents that are sensitive to heat orradiation, for example infra-red, visible light, or ultra-violetradiation. The polymer material can be a curable material applied in aliquid form that hardens when the cross-linking agents are activated,for example with exposure to radiation or heat. When a molding device,such as the first stamp 80 or multi-level second stamp 82 having aninverse micro-channel structure is applied to liquid curable material ina curable layer coated on the substrate 10 and the cross-linking agentsin the curable material are activated, the liquid curable material inthe curable layer is hardened into a cured layer having micro-channelswith the inverse structure of the stamp. The liquid curable materialscan include a surfactant to assist in controlling coating. Materials,tools, and methods are known for embossing coated liquid curablematerials to form cured layers having conventional single-layermicro-channels.

Similarly, curable inks useful in the present invention are known andcan include conductive inks having electrically conductivenano-particles, such as silver nano-particles. The electricallyconductive nano-particles can be metallic or have an electricallyconductive shell. The electrically conductive nano-particles can besilver, can be a silver alloy, or can include silver.

Curable inks provided in a liquid form are deposited or located inmicro-channels and cured, for example by heating or exposure toradiation such as infra-red, visible light, or ultra-violet radiation.The curable ink hardens to form the cured ink that makes up micro-wires.For example, a curable conductive ink with conductive nano-particles islocated within micro-channels and heated to agglomerate or sinter thenano-particles, thereby forming an electrically conductive micro-wire.Materials, tools, and methods are known for coating liquid curable inksto form micro-wires in conventional single-layer micro-channels. Thecurable conductive ink is not necessarily electrically conductive beforeit is cured.

It has been experimentally demonstrated that micro-channels having awidth of four microns formed in a cured layer with a depth having arange of about four microns to twelve microns over a conductive layercan be filled with liquid curable conductive inks containing silvernano-particles and cured with heat to form micro-wires thatconduct-electricity to the conductive layer, thus enabling electricalconduction between separate micro-wires in a cured layer through theconductive layer. Oxygen plasmas that thin the cured layer by two toeight microns have been shown to enable the formation of micro-wiresthat are in electrical contact with the underlying conductive layer. Ithas also been experimentally demonstrated that micro-wires formed in amicro-channel in a bottom layer can be contacted with a micro-wireformed in a micro-channel in a layer coated over the bottom layer toform an electrically continuous conductive micro-structure.

According to various embodiments of the present invention, substrate 10is any material having a surface on which a cured layer can be formed.Substrate 10 can be a rigid or a flexible substrate made of, forexample, a glass, metal, plastic, or polymer material, can betransparent, and can have opposing substantially parallel and extensivesurfaces. Substrates 10 can include a dielectric material useful forcapacitive touch screens and can have a wide variety of thicknesses, forexample 10 microns, 50 microns, 100 microns, 1 mm, or more. In variousembodiments of the present invention, substrates 10 are provided as aseparate structure or are coated on another underlying substrate, forexample by coating a polymer substrate layer on an underlying glasssubstrate.

Substrate 10 can be an element of other devices, for example the coveror substrate of a display or a substrate, cover, or dielectric layer ofa touch screen. In an embodiment, a substrate 10 of the presentinvention is large enough for a user to directly interact therewith, forexample using an implement such as a stylus or using a finger or hand.Methods are known in the art for providing suitable surfaces on which tocoat a single curable layer. In a useful embodiment, substrate 10 issubstantially transparent, for example having a transparency of greaterthan 90%, 80% 70% or 50% in the visible range of electromagneticradiation.

Electrically conductive micro-wires and methods of the present inventionare useful for making electrical conductors and busses for transparentmicro-wire electrodes and electrical conductors in general, for exampleas used in electrical busses. A variety of micro-wire or micro-channelpatterns can be used and the present invention is not limited to any onepattern. Micro-wires can be spaced apart, form separate electricalconductors, or intersect to form a mesh electrical conductor on or in alayer. Micro-channels can be identical or have different sizes, aspectratios, or shapes. Similarly, micro-wires can be identical or havedifferent sizes, aspect ratios, or shapes. Micro-wires can be straightor curved.

In some embodiments, a micro-channel is a groove, trench, or channelformed in a cured layer and having a cross-sectional width less than 20microns, for example 10 microns, 5 microns, 4 microns, 3 microns, 2microns, 1 micron, or 0.5 microns, or less. In an embodiment, amicro-channel depth is comparable to a micro-channel width.Micro-channels can have a rectangular cross section, as shown in theFigures. Other cross-sectional shapes, for example trapezoids, are knownand are included in the present invention. The width or depth of a layeris measured in cross section.

In various embodiments, cured inks can include metal particles, forexample nano-particles. The metal particles can be sintered to form ametallic electrical conductor. The metal nano-particles can be silver ora silver alloy or other metals, such as tin, tantalum, titanium, gold,copper, or aluminum, or alloys thereof. Cured inks can includelight-absorbing materials such as carbon black, a dye, or a pigment.

In an embodiment, a curable ink can include conductive nano-particles ina liquid carrier (for example an aqueous solution including surfactantsthat reduce flocculation of metal particles, humectants, thickeners,adhesives or other active chemicals). The liquid carrier can be locatedin micro-channels and heated or dried to remove liquid carrier ortreated with hydrochloric acid, leaving a porous assemblage ofconductive particles that can be agglomerated or sintered to form aporous electrical conductor in a layer. Thus, in an embodiment, curableinks are processed to change their material compositions, for exampleconductive particles in a liquid carrier are not electrically conductivebut after processing form an assemblage that is electrically conductive.

Once deposited, the conductive inks are cured, for example by heating.The curing process drives out the liquid carrier and sinters the metalparticles to form a metallic electrical conductor. Conductive inks areknown in the art and are commercially available. In any of these cases,conductive inks or other conducting materials are conductive after theyare cured and any needed processing completed. Deposited materials arenot necessarily electrically conductive before patterning or beforecuring. As used herein, a conductive ink is a material that iselectrically conductive after any final processing is completed and theconductive ink is not necessarily conductive at any other point in themicro-wire formation process.

In various embodiments of the present invention, micro-channels ormicro-wires have a width less than or equal to 10 microns, 5 microns, 4microns, 3 microns, 2 microns, or 1 micron. In an example andnon-limiting embodiment of the present invention, each micro-wire isfrom 10 to 15 microns wide, from 5 to 10 microns wide, from one micronto five microns wide or from one/half micron to one micron wide. In someembodiments, micro-wires can fill micro-channels; in other embodimentsmicro-wires do not fill micro-channels. In an embodiment, micro-wiresare solid; in another embodiment micro-wires are porous.

Micro-wires can include metal, for example silver, gold, aluminum,nickel, tungsten, titanium, tin, or copper or various metal alloysincluding, for example silver, gold, aluminum, nickel, tungsten,titanium, tin, or copper. Micro-wires can include a thin metal layercomposed of highly conductive metals such as gold, silver, copper, oraluminum. Other conductive metals or materials can be used.Alternatively, micro-wires can include cured or sintered metal particlessuch as nickel, tungsten, silver, gold, titanium, or tin or alloys suchas nickel, tungsten, silver, gold, titanium, or tin. Conductive inks canbe used to form micro-wires with pattern-wise deposition or pattern-wiseformation followed by curing steps. Other materials or methods forforming micro-wires, such as curable ink powders including metallicnano-particles, can be employed and are included in the presentinvention.

Electrically conductive micro-wires of the present invention can beoperated by electrically connecting-layer micro-wires through connectionpads and electrical connectors to electrical circuits that provideelectrical current to micro-wires and can control the electricalbehavior of micro-wires. Electrically conductive micro-wires of thepresent invention are useful, for example in touch screens such asprojected-capacitive touch screens that use transparent micro-wireelectrodes and in displays. Electrically conductive micro-wires can belocated in areas other than display areas, for example in the perimeterof the display area of a touch screen, where the display area is thearea through which a user views a display.

Methods and devices for forming and providing substrates and coatingsubstrates are known in the photo-lithographic arts. Likewise, tools forlaying out electrodes, conductive traces, and connectors are known inthe electronics industry as are methods for manufacturing suchelectronic system elements. Hardware controllers for controlling touchscreens and displays and software for managing display and touch screensystems are all well known. All of these tools and methods can beusefully employed to design, implement, construct, and operate thepresent invention. Methods, tools, and devices for operating capacitivetouch screens can be used with the present invention.

The present invention is useful in a wide variety of electronic devices.Such devices can include, for example, photovoltaic devices, OLEDdisplays and lighting, LCD displays, plasma displays, inorganic LEDdisplays and lighting, electrophoretic displays, electrowettingdisplays, dimming mirrors, smart windows, transparent radio antennae,transparent heaters and other touch screen devices such as resistivetouch screen devices.

The invention has been described in detail with particular reference tocertain embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

PARTS LIST

-   -   D1 direction    -   D2 direction    -   5 imprinted micro-wire structure    -   10 substrate    -   12 bottom layer    -   14 connecting layer    -   15 multi-layer    -   16 top layer    -   18 connecting mid-layer    -   19 mid-layer    -   20 top-layer micro-channel    -   22 top-layer micro-wire    -   26 top electrode    -   30 connecting-layer micro-channel    -   32 connecting-layer micro-wire    -   34 connecting mid-layer micro-wire    -   40 edge micro-channel    -   41 multi-layer micro-channel    -   42 edge micro-wire    -   43 multi-layer micro-wire    -   44 second edge micro-wire    -   46 bottom electrode    -   50 bottom-layer micro-channel    -   52 bottom-layer micro-wire    -   54 mid-layer micro-wire    -   60A row connection pad    -   60B column connection pad    -   62 connecting wire    -   70 central area    -   72 edge area    -   73 second edge area    -   74 first substrate edge    -   76 second substrate edge    -   78 micro-wire bridge    -   80 first stamp    -   81 deep protrusion    -   82 multi-level second stamp    -   83 shallow protrusion    -   84 deep-protrusion depth    -   85 shallow-protrusion depth    -   86 second stamp    -   87 third stamp    -   89 protrusion    -   90 radiation    -   92 plasma    -   94 thinning depth    -   100 provide substrate step    -   105 provide stamps step    -   106 provide stamps step    -   110 form bottom layer step    -   115 imprint bottom-layer micro-channels step    -   120 cure bottom-layer micro-channels step    -   130 deposit conductive ink in bottom-layer micro-channels step    -   135 cure conductive ink in bottom-layer micro-channels step    -   210 form connecting layer step    -   215 imprint connecting-layer micro-channels step    -   220 cure connecting-layer micro-channels step    -   225 optional plasma-treat connecting-layer micro-channels step    -   230 deposit conductive ink in connecting-layer micro-channels        step    -   235 cure conductive ink in connecting-layer micro-channels step    -   310 form top layer step    -   315 imprint top-layer micro-channels step    -   320 cure top-layer micro-channels step    -   325 optional plasma-treat top-layer micro-channels step    -   330 deposit conductive ink in edge and top-layer micro-channels        step    -   335 cure conductive ink in top-layer micro-channels step    -   410 form multi-layer step    -   415 imprint multi-layer micro-channels with multi-level stamp        step    -   420 cure multi-layer micro-channels step    -   425 optional plasma-treat multi-layer micro-channels step    -   430 deposit conductive ink in multi-layer micro-channels step    -   435 cure conductive ink in multi-layer micro-channels step

1. A method of making a micro-wire structure, comprising: providing a substrate having an edge area and a central area separate from the edge area; providing first, second, and third different stamps; providing a curable bottom layer in relation to the substrate; forming an imprinted bottom-layer micro-channel in the curable bottom layer by at least imprinting the curable bottom layer with the first stamp in at least a portion of the central area and in at least a portion of the edge area and curing the curable bottom layer, the bottom-layer micro-channel extending from the central area into the edge area; locating a curable electrical conductor in the bottom-layer micro-channel and curing the curable electrical conductor to form a bottom-layer micro-wire in the bottom-layer micro-channel, the bottom-layer micro-wire extending from the central area into the edge area; providing a curable connecting layer adjacent to and in contact with the cured bottom layer and the bottom-layer micro-wire; forming an imprinted connecting-layer micro-channel in the curable connecting layer by at least imprinting the curable connecting layer with the second stamp over at least a portion of the bottom-layer micro-channel in at least a portion of the edge area and curing the curable connecting layer; forming a connecting-layer micro-wire in the connecting-layer micro-channel contacting at least a portion of the bottom-layer micro-wire; providing a curable top layer adjacent to and in contact with the cured connecting layer and the connecting-layer micro-wire; forming an imprinted edge micro-channel in the curable top layer by at least imprinting the curable top layer with the third stamp over at least a portion of the connecting-layer micro-channel in at least a portion of the edge area and forming an imprinted top-layer micro-channel in the curable top layer by at least imprinting the curable top layer with the third stamp separate from the bottom-layer micro-channel and over at least a portion of the bottom-layer micro-channel in at least a portion of the central area and curing the curable top layer; forming an edge micro-wire in the edge micro-channel contacting at least a portion of the connecting-layer micro-wire and forming a top-layer micro-wire in the top-layer micro-channel that is electrically isolated from the edge micro-wire, the connecting-layer micro-wire, and the bottom-layer micro-wire; and wherein the bottom-layer micro-wire in the central area is electrically connected to the edge micro-wire in the edge area and is electrically isolated from the top-layer micro-wire.
 2. The method of claim 1, wherein the substrate has at least one edge and the edge area is adjacent to the edge.
 3. The method of claim 1, wherein a portion of the edge micro-wire forms at least a portion of a connection pad.
 4. The method of claim 3, wherein the connection pad further includes a plurality of micro-wires.
 5. The method of claim 1, further including forming a plurality of edge micro-wires electrically connected through a corresponding plurality of connection micro-wires to a corresponding plurality of bottom-layer micro-wires.
 6. The method of claim 5, further including forming a plurality of top-layer micro-wires electrically isolated from the edge micro-wires.
 7. The method of claim 6, wherein the top-layer micro-wires and the bottom-layer micro-wires form a two-dimensional array of overlapping micro-wires.
 8. The method of claim 6, wherein the substrate has at least first and second edges and at least some of the plurality of edge micro-wires are located in an edge area adjacent to the first edge and at least some of the plurality of top-layer micro-wires extend into a second edge area adjacent to the second edge and separate from the central area.
 9. The method of claim 8, wherein the edge micro-wires are in the edge area and the top-layer micro-wires extend into the edge area.
 10. The method of claim 9, wherein portions of the top-layer micro-wires are interdigitated between the edge micro-wires in the edge area.
 11. The method of claim 1, wherein the step of forming the imprinted connecting-layer micro-channel further includes contacting the bottom-layer micro-wire with the second stamp.
 12. The method of claim 1, wherein the step of forming the imprinted edge micro-channel further includes contacting the connecting-layer micro-wire with the third stamp.
 13. The method of claim 1, further including removing a portion of the cured connecting layer or removing a portion of the cured top layer.
 14. The method of claim 13, further including removing the portion of the cured second or cured top layer by treating the cured second or cured top layer with a plasma treatment.
 15. The method of claim 13, further including thinning the cured second or cured top layer by a thinning depth.
 16. The method of claim 15, wherein the thinning depth is less than the difference between the depth of the cured second or cured top layer and the depth of any micro-channels in the corresponding cured second or cured top layer.
 17. The method of claim 1, wherein the bottom and connecting layers include cross-linkable material and further including cross linking the cross-linkable first-layer material to the cross-linkable second-layer material or wherein the connecting and top layers include cross-linkable material and further including cross linking the cross-linkable second-layer material to the cross-linkable third-layer material.
 18. The method of claim 1, wherein either: a) the curable bottom layer includes first curable material and further including locating the first stamp in contact with the first curable material and only partially curing the first curable material, wherein the curable connecting layer includes second curable material and further including locating the second stamp in contact with the second curable material, and at least partially curing both the first curable material and the second curable material in a common step; or b) the curable connecting layer includes second curable material and further including locating the second stamp in contact with the second curable material and only partially curing the second curable material, wherein the curable top layer includes third curable material and further including locating the third stamp in contact with the third curable material, and at least partially curing both the second curable material and the third curable material in a common step.
 19. The method of claim 1, further including either: a) depositing first conductive ink in the bottom-layer micro-channel and at least partially curing the first conductive ink, further including depositing second conductive ink in the connecting-layer micro-channel and at least partially curing the first conductive and second conductive ink in a common step; or b) depositing first conductive ink in the connecting-layer micro-channel and at least partially curing the first conductive ink, further including depositing second conductive ink in the edge micro-channel and at least partially curing the first conductive and second conductive ink in a common step.
 20. The method of claim 19, wherein the first and second conductive inks include electrically conductive particles and further including sintering, welding, or agglomerating electrically conductive particles in the second conductive ink to electrically conductive particles in the first conductive ink. 